The present invention relates to an adhesive composition usable for a pre-applied application in flip chip mounting of semiconductor chips, an electronic component with adhesive layer and an electronic device using the adhesive composition, and a production method thereof.
As a mounting technology of a semiconductor chip, flip chip technology, which directly connects a semiconductor chip on a board, is known. In flip chip mounting, a semiconductor chip is connected to a wiring board through an electrode (bump) formed on the element-formed face (the active circuit face) of a semiconductor chip. An underfill material, which is an adhesive resin composition, is generally filled between the bonding faces for the purpose of reinforcement of bonding sites and improvement in bonding reliability.
Capillary underfilling is known as a method of filling an underfill material. This method comprises the steps of making an electrical connection of a wiring board and an electrode on a chip, applying a liquid resin composition on one or more sides of the chip, and allowing the resin composition to flow into the gap between the wiring board and the chip by capillary action. Upon curing, the underfill material acts as an encapsulant. However, the capillary underfilling system has the disadvantage of requiring more time than optimally feasible for sealing because it is difficult to uniformly inject the resin into the space between fine electrodes in a short time.
To solve this problem, a method is known, wherein an adhesive in the form of a film or paste is placed on a board, subsequently a semiconductor chip is mounted, and electrode bonding and sealing are carried out at the same time. This method requires a step of providing an adhesive on a board in the production of an electronic device.
From a viewpoint of further foreshortening the mounting process, a method using the pre-applied underfill sealant (PAUF) is known. This method is characterized in using an electronic component equipped with a B-staged adhesive composition beforehand in producing an electronic device. B-staged means that any solvent in the adhesive composition is evaporated off and/or the adhesive partially cured, so that the adhesive composition is not tacky. For instance, a wafer with an adhesive layer is used, which has a B-staged adhesive composition on one face of the wafer beforehand. Then, the wafer with the adhesive layer is separated into semiconductor chips by dicing, and a separated semiconductor chip is mounted and bonded on a board to produce an electronic device. Alternatively, an electronic device may be produced by using a wiring board equipped with a B-staged adhesive composition. This method facilitates an increase in the UPH (i.e. unit per hour: production volume per hour) for manufacturers of wiring boards because the step of applying a resin composition onto the wiring board can be omitted in producing an electronic device. Also, when semiconductor chips are multistacked, using the pre-applied underfill sealant has merit since it is easy to handle; for example, there is no need for a step of applying the adhesive and no operational variation in the applied adhesive.
As an adhesive for underfill, adhesives comprising an epoxy resin have been known. A wide variety of epoxy resins have been developed and used because the adhesives comprising the epoxy resin have an advantage in high adhesiveness for various substrates, and excellent mechanical strength and insulation.
However, an adhesive containing an epoxy resin has a short pot life due to the gradual progression of a curing reaction. For this reason, an electronic component equipped with an adhesive containing an epoxy resin as a pre-applied underfill sealant is not suitable for a method undergoing several steps afterward for producing a semiconductor. There are also many problems on setting a condition for a mounting process in the flip chip technique. For example, using an adhesive comprising an epoxy resin requires a long time for thermal compression bonding because an epoxy resin needs a long curing time, and it is difficult to control a temperature in each step of mounting because heat of the reaction is high. Furthermore, an adhesive containing an epoxy resin has a high concentration of chlorine derived from the production of source materials, which may corrode the metal in use for an electronic material.